Field of the Invention
The present invention concerns a contouring processor, a method and a radiotherapy apparatus as well as a storage medium encoded with programming instructions for acquiring contour data to determine a target volume for configuring a radiotherapy apparatus, such as a particle generator.
Description of the Prior Art
Linear accelerators are used, among other things, in radiation therapy for treating tissue, particularly tumor diseases. Here charged particles are usually accelerated to high energies, formed into a particle beam and fed via a high energy beam transporting system to one or more radiotherapy devices. The target volume to be irradiated is then irradiated using the particle beam of one of these radiotherapy machines.
Before the linear accelerator or another radiotherapy device can be put into operation, it must first be configured, among other things, as to which target volume is to be irradiated. For this purpose, a computed tomography (CT) scan of the relevant region of the patient is generally performed in advance. The cross-sectional images thus obtained are transmitted via a network to a computer. The contours of the regions to be irradiated are marked on these cross-sectional images, as well as organs at risk such as the spinal canal, liver, kidneys, lenses in the eyes, etc.
The contoured cross-sectional images or volumes can be displayed in a two-dimensional or three-dimensional manner. The contoured regions are then assigned a target dose value that is selected such that the tumor tissue is irradiated as fully as possible and healthy surrounding tissue is damaged as little as possible. Contour data containing instruction sets is then calculated from the contour-enhanced cross-sectional images and transmitted by a planning system having a device configuration computer for the radiotherapy device. Conventionally, the doctor or technician at the device configuration computer has been tasked with determining an optimum irradiation technique, i.e. the number of fields, their size, shape and incident beam angle, and with determining the resulting dose distribution in the patient. Computer-based systems assist with this task, e.g. by the use of a beam-based display (beam's eye view). The basic goal is to irradiate the tumor as homogeneously and adequately as possible while causing minimum damage to the organs at risk and surrounding healthy tissue. The accelerator, or more specifically the radiotherapy device then performs the irradiation in a downstream time phase or later.
In the prior art, it is known to compare a large number of dose volume histograms and use this as a basis for calculating the respective target dose. However, the user receives no indications for contouring.
In addition, contouring tools are known that suggest contours, particularly for organs at risk, on the basis of landmarks. However, landmark-based contouring tools are unsuitable for contouring (tumor) tissue to be irradiated and therefore for determining the target volume (even though they can indeed be additionally used as aids for defining the position of the organs at risk). This is because the site of tumor tissue is generally not landmark-dependent (and has no particular distance from the spinal column, bones or an easily identifiable organ).
Contour data have conventionally been entered locally on-site and without matching that data with other (external) data sources, and manually by the doctor. This has a high potential for error. It is obvious that incorrect contour data has unacceptable consequences, as in some circumstances too much healthy or too little malignant tissue will be irradiated.